client.go

package main
import (
    "net/http"
	"fmt"
	"time"
    opentracing "github.com/opentracing/opentracing-go"
    "github.com/opentracing/opentracing-go/ext"

	jaeger "github.com/uber/jaeger-client-go"
	config "github.com/uber/jaeger-client-go/config"
)
func main(){
tracer := opentracing.GlobalTracer()
cfg := &config.Configuration{
	ServiceName: "client",
	Sampler: &config.SamplerConfig{
		Type:  "const",
		Param: 1,
	},
	Reporter: &config.ReporterConfig{
		LogSpans: true,
	},
}
//1
tracer, closer, err := cfg.NewTracer(config.Logger(jaeger.StdLogger))
defer closer.Close()
if err != nil {
	panic(fmt.Sprintf("ERROR: cannot init Jaeger: %v\n", err))
}

//2
clientSpan := tracer.StartSpan("clientspan")
defer clientSpan.Finish()
time.Sleep(time.Second)

url := "http://localhost:8083/publish"
req, _ := http.NewRequest("GET", url, nil)

// Set some tags on the clientSpan to annotate that it's the client span. The additional HTTP tags are useful for debugging purposes.
ext.SpanKindRPCClient.Set(clientSpan)
ext.HTTPUrl.Set(clientSpan, url)
ext.HTTPMethod.Set(clientSpan, "GET")

// Inject the client span context into the headers
//3
tracer.Inject(clientSpan.Context(), opentracing.HTTPHeaders, opentracing.HTTPHeadersCarrier(req.Header))
resp, _ := http.DefaultClient.Do(req)
fmt.Println(resp)
}